Types of Evidence Flashcards
What type of fingerprints are taken when collected in a controlled environment?
Full image of fingerprints. Nail line to nail line for each finger.
The ability to collect/lift fingerprints on a crime scene is dependent upon:
-Material surface
-Moisture/Temperature
-Sliding/Smudges
A lifted fingerprint is referred to as what?
A Latent Fingerprint
A latent fingerprint is a partial or full print?
Partial
What is the most common technique to locate and lift fingerprints?
Dusting
Dusting
Soft brush, dust a graphite powder over a surface, oil from fingerprints adheres to the powder, life the print with an adhesive
National database for fingerprints
AFIS. Automated Fingerprints Identification System
Who maintains AFIS?
FBI
Limitations of Fingerprint Evidence
-Number of fingerprints
-Quality of latent
-Time consuming
Strengths of AFIS
-75% of adults have a fingerprint in the system
-Comparing a full image to another full image is very effective in the system
Weaknesses of AFIS
Comparing a full image to a partial print - a pointer system, still requires an expert to make direct matches
Most common Impression Evidence
-Shoe markings/footprints
-Tire markings
Shoe markings are collected as what?
A cast
Strengths of Impressions of Shoe Markings
-People tend to keep their shoes for a really long time
-Bottom of shoe is very unique
-If you can find the suspects show you can do one to one comparison with the wear marks
Weakness of Impressions of Shoe Markings
-No database for shoes
-Only works for one to one comparison, meaning you have to find the shoe in order for this to work
Strengths of Tire Impressions
-through expert determine width of the ture
-manufacture and model of tire by the tread
-if you can find the suspect tire you can compare to tire and do a one to one comparison
Limitations of Tire Impressions
-No national tire database
-Only be used in a one to one comparison, meaning you must identify tire
-In a skid, you loose the ability to make a one to one comparison
Ballistic Evidence
Captures and digitally photographs the fine markings, stripes and other markings on bullets and cartridges that are created during the process of firing a gun
National database for bullets and casings
NIBIN. National Integrated Ballistic Information Network
Who maintains NIBIN?
ATF. Alcohol, Tobacco and Firearms
Cartridge Components
-Projective (bullet)
-Casing
-Propellant
-Ignition (primer)
Cartridge
An unfired round of ammunition
Bullet/Projectile
The projectile, comes out of the gun
Casing
To hold the bullet in the case before it is fired
Primer
The bottom of the casing, small silver disk, ignition switch
Two types of handguns
-Semi-Automatic Pistol
-Revolver
Rifiling Effect
Grooves that are carved into the barrel of the gun, spins the bullet that allows the bullet to travel in a straight line, increases the accuracy
3 Points of Comparison of a Semi-Automatic Pistol
-Firing pin marks (bottom of casing)
-Ejection marks (side of casing)
-Bullet (lands and grooves)
What comparison of a semi-automatic pistol easiest to compare?
Primer/Firing Pin Marks
Does the casing eject or stay in a semi-automatic pistol?
Eject
Does the casing eject in a revolver?
No, it stays in the cylinder of the gun
What is the only point of comparison on a revolver?
Land and groove marks on the bullet
T/F. Revolvers have a riffling effect.
True
Limitation of a revolver
Only 5 -6 shots can be made before reloading
How do bullets eliminate the possibility of comparison?
When bullets are fired they become compressed and distorted after coming into contact with a hard object
Do shot guns have a rifling effect?
No
What is the point of comparison for a shotgun?
The firing pin marking on the primer
How does a casing eject in a shotgun?
Requires manually pumping
T/F. A rifle has the same points of comparison as a semi-automatic pistol.
True
T/F. Submachine guns work the same way as a rifle
F. They work the same way as a semi-automatic pistol.
Are submachine guns accurate?
No, due to their short barrel
How can you usually tell when a submachine gun was used in a crime?
There are lots of rounds among the scene
T/F. Gun shot residue is traceable
F. It is completely untraceable
What does gun residue tell us?
Tells us when someone has recently fired a gun
When is gun residue most reliable?
Most reliable when a person is stopped right after the crime and close the crime scene
